1. Field of the Invention
The present invention relates to an electrochemical cell and a process having a split fluid and current feed.
2. Description of the Related Art
In the design of an internal distribution manifold electrolyzer, the cross-sectional area of the internal manifolds is calculated to maintain a minimum fluid velocity to insure minimum pressure drop from point of entry to the last cell in the electrolyzer. As the number of cells per electrolyzer increases, the cross-sectional area increases to account for the increased flow and the increased length of the manifold. This situation worsens when one of the fluids becomes a two-phase flow in the catholyte exit. In a two-phase flow system, as the pressure in the manifold decreases, the total volumetric flow increases due to gas expansion.
A typical internal manifold electrolyzer of the prior art is shown generally at 10 in FIG. 1A. FIG. 1A is a cut-away, cross-sectional view of FIG. 1, which is a front end view of a multi-cell, bi-polar electrolyzer of the prior art. Each electrochemical cell is shown at 1 in FIG. 1A. The electrolyzer shown in FIG. 1 includes a current bus 28, in which are formed anode-side inlet manifold 3, anode-side outlet manifold 7, cathode side inlet manifold 11 and cathode-side outlet manifold 15. Inlet fluid is supplied to electrolyzer 10 from one side only, such as at inlet 13 in FIG. 1A, and a blind flange 19 is typically installed at the opposite end of the manifold. Fluid flows from each electrochemical cell and into outlet manifold 15 and exits the electrolyzer at one end only, as at outlet 23 as shown in FIG. 1A. The other end of the outlet manifold is closed off with a blind flange 25.
The electrolyzer design of FIGS. 1 and 1A requires that the inlet and outlet manifolds be of large cross-sectional area to reduce fluid pressure drop. This requirement is to ensure equal fluid distribution to and from each electrochemical cell. Failure to maintain almost equal pressures throughout the manifold results in unequal flow to and from all of the cells. Such unequal flow distribution to and from each cell results in uneven performance of the cells.
Since the electrolyzer shown in FIGS. 1 and 1A requires four independent manifolds (an inlet and an outlet manifold for the anolyte and the catholyte, respectively), these manifolds consume a large fraction of the area of each current distributor plate, thus decreasing the electrolyzer active area. Such an internal manifold electrolyzer uses only 65% to 70% of its total area as active area, the balance being used to accommodate the manifolds. In addition, as the cross-sectional area of the manifolds increases, the potential for internal shunt current within each manifold also increases.
Thus, there exists a need for reducing the internal shunt current within each manifold while reducing the cross-sectional area required of the internal manifolds of an internal distribution electrolyzer, thereby increasing the active area in the electrolyzer without increasing the overall area of the current distributors.
FIG. 2 is a plan view showing the current feed to multi-cell, bi-polar electrolyzer 10 of the prior art, In the electrolyzer of the prior art of FIG. 2, current is fed to the anode-side of the electrolyzer through an electrical connection 29 and through anode-side current bus 28. Current is removed from the cell through cathode-side current bus 30 and through an electrical connection 31. In a multi-cell, bi-polar electrolyzer, the overall voltage of the electrolyzer is the product of the voltage of each individual cell and the number of cells. Thus, as it becomes necessary to add individual cells in the electrolyzer, the overall voltage of the electrolyzer increases. The higher the overall voltage of the electrolyzer gets, the greater the propensity for internal shunt currents to occur.